Color is fundamental to painting yet it's easy to be seduced by it and never truly master it. By limiting the number of colors you use, you get to truly know the characteristics of each and are able to use it to its full potential.
This painting was created using only lemon yellow, phthalo blue, burnt sienna, and titanium white (acrylics). The first three are transparent colors, perfect for glazing. The last is a strongly opaque color, and mixing a little with the others makes them opaque too. (See How to Test if a Paint Color is Opaque or Transparent.)
Mixing and glazing with this small number of colors doesn't mean you're severely limited in the colors you can produce. For starters, lemon yellow and phthalo blue produce a glorious range of greens, while burnt sienna and phthalo blue mixed together give a strong dark. See this photo for a page from my sketchbook where I've played with mixing these colors, for an idea of the range of colors you can produce.
Note: The color variation between the various steps is the result of camera difficulties, not a change in paint color.
